A computer worm that ferrets out passwords managed to stow away on laptops aboard the International Space Station, NASA has confirmed. It is not the first time a NASA computer has become infected.

SpaceReg.com identified the infection as W32.TGammima.AG, a worm that spreads by copying itself to removable media devices. Once in place, it steals passwords to various online games, according to anti-virus software provider Symantec, which first spotted the worm 12 months ago.

"This is not the first time we have had a worm or a virus," a NASA spokesman told Wired News. "It's not a frequent occurrence, but this isn't the first time."

The infected machines were not considered mission critical, meaning they weren't responsible for command and control. The NASA spokesman was unable to say if the infected laptops were connected to mission-critical systems.

Exactly how computers aboard the tightly controlled space station get infected by a common internet parasite is a bit of a head scratcher. Because more than one laptop was infected, it's reasonable to assign blame to an internal network or thumb drive. Then again, floating around in outer space can be a lonely experience, so other forces may have been at work.